Days after choking smog blanketed China's capital, the country's premier-designate added his voice to appeals to curb the toxic haze, but he offered few specifics and said there was no quick fix.

The comments from Vice Premier Li Keqiang, who is expected to take over as premier at a national congress in March, marked the first time a member of the ruling Communist Party's seven-member Politburo Standing Committee has addressed the pollution levels that reached record levels during the weekend.

Conditions had eased somewhat by Tuesday, but the hazardous air sparked angry comments from some of Beijing's 20 million residents and enlivened a usually compliant state media to criticize government inaction.

"There has been a long-term buildup to this problem, and the resolution will require a long-term process. But we must act," state radio cited Li as saying on Tuesday, three days after the pollution measures soared past previous records.

"On the one hand, we have to increase the strength of environmental management and other official tasks, and on the other hand we must remind the public to strengthen personal protection. This situation requires the awareness and participation of all people and our joint management," he said.

Emissions from factories and heating plants, fumes from millions of vehicles and the burning of coal bricks to heat homes often conspire to blanket the city in a pungent haze that can become trapped over the city when weather conditions are right.

Air quality in Beijing was far above hazardous levels over the weekend, reaching 755 on Saturday on an index that measures particulate matter in the air with a diameter of 2.5 micrometers. A level above 300 is considered hazardous, while the World Health Organisation recommends a daily level of no more than 20.

Particulate matter with a 2.5 micrometer diameter, known as PM2.5, can cause cardiopulmonary disease, lung cancer and acute respiratory infection, according to the Journal of Toxicology and Environmental Health.

Li praised the government for openly publishing data on the PM2.5 particulates in a "timely and realistic" manner, although it made the change only last year after public pressure in response to a popular following of the index published by the U.S. Embassy in Beijing.

However, some observers said the government has been relatively quick to admit to the scale of the air pollution problem in the capital, in part because it is concerned about potential unrest from growing pollution woes across the country, but also because air quality cannot be concealed from the public eye despite strictly controlled media.

The Beijing branch of China's environmental watchdog said on its microblog on Monday that it had implemented a one-day emergency pollution reduction plan, which aimed to reduce the number of government cars on roads and to cut emissions at 54 factories by 30 percent.

Digging and demolition work at 28 construction sites would be temporarily halted, it said, but offered no details on the projects or factories involved in the plan.

Ma Jun, an environmentalist who founded the Institute of Public and Environmental Affairs, said the government's handling of the recent smog-wave had been "unprecedented" in its transparency.

"The first step is to tell people the truth, and to put people's health ahead of the face of the government. To have the courage to face reality, it's the precondition for any meaningful solution," Ma told Reuters.

But he said over the long run officials must look beyond the capital for a solution for cleaner Beijing air.

"The whole region has been too dependent on heavily polluting industry. The discharge volume is way beyond environmental capacity, so we need to change the economic structure, and change the growth model," Ma said.

Air pollution readings still hovered at unhealthy levels on Tuesday, according to U.S. Embassy data.

The toxic air has not stifled the wit of Beijing residents, many of whom resorted to sarcasm in an effort to cope with the smog.

One Internet user recorded new lyrics to a well-known ballad titled "Beijing, Beijing", replacing emotional references to the city with accounts of its smog-stricken skies in a video that had been viewed hundreds of thousands of times on China's video-sharing site Youku.

Others vented on microblogs.

"I love our city, but I refuse to be a human vacuum cleaner," said one posting.